Halogenated aromatic hydrocarbons (HAHs) are a diverse group of widespread anthropogenic environmental contaminants (Chemosphere 37, 1731-1741). These organochlorines compounds have been found widespread in ambient air (Environ Sci Technol 38, 4937-4944), stack flue gas (Chemosphere 50, 1123-1129), sediment (Chemosphere 31, 2863-2872), fish (Environ Pollut 141, 381-386), blood and placentas (Chemosphere 54, 1459-1473) as well as breast milk (Food Chem Toxicol 42, 1299-1308; J Hazard Mater 121, 1-10), and tend to bioaccumulate in the food chain. Some HAHs are highly toxic, and most of these compounds, such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs), cause toxicity by binding to and activating the aryl hydrocarbon receptor (Ah receptor or AhR), in which 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is the most extensively studied one and has therefore become a prototype for this class of toxic environmental contaminants.
One of the recent techniques for detection and quantification of these toxic compounds is high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS), which is costly and time-consuming. As an alternative, the chemical activated luciferase expression (CALUX) bioassay is an in vitro luciferase-reporter-gene assay for detecting the Toxic Equivalents (TEQ) levels of these toxic compounds based on their ability to bind and activate AhR. U.S. Pat. No. 5,854,010 describes a recombinant cell line, the mouse H1L1.1 cell line, made by using generic engineering techniques for inserting dioxin responsive elements (DREs) upstream of a luciferase report gene and then transfecting the resultant recombinant expression plasmid into mouse hepatoma cells. Garrison et al. describes species-specific recombinant cell lines as bioassay systems for the detection of TCDD-like chemicals (Fundam Appl Toxicol 30, 194-203). However, these conventional bioassays rely on selection of stable responsive cell lines which can maintain their responsiveness to the toxic compounds for an expended period; however, most of the stable cell lines would gradually lose such responsiveness during cell passages.